Process for coating drawn metal parts

ABSTRACT

Process for using coating guns to apply a conductive layer to the inside of battery cans moving on a conveyor with intermittent move and dwell times. Pats are automatically inspected. If a layer is defective due to a disabled coating gun, the process includes firing another coating gun at twice its normal firing rate and/or shifting its position so that it does the job of two coating guns.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority of provisional application Ser. No.60/437,531 filed Dec. 31, 2002.

BACKGROUND OF THE INVENTION

This invention relates to a high volume manufacturing process forcontinuously coating and inspecting drawn metal parts as part of acontinuous series of operations to produce finished drawn metal parts.An example of high volume manufacturing of drawn metal parts is theproduction of battery cans, which are used as the primary battery casingfor commercial cells, such as A, AA, AAA, C, D, F, M, etc.

Manufacturing of battery cans according to the prior art is generallyaccomplished by a batch and queue process in the following manner. Aredraw press accepts narrow strip stock from a payoff reel and performsblanking, cupping and subsequent redraw operations. The entire batterycan is manufactured in each stand-alone redraw press and the cans arecollected in bulk in containers. The press operator and/or toolmakermanually inspect the dimensional and cosmetic attributes of the can. Apre-determined number of cans are removed randomly and inspected. Nextthe containers of parts from the press are moved to a staging area neara washer/dryer machine. The washer/dryer, which removes the drawinglubricant, is typically a rotary bulk washer with a cob dryer. Anoperator feeds the cans into the inlet of the washer. The washed cansare caught in bulk hoppers or cartons.

Next the washed cans are moved to a staging area near a coating machine.The coating machines apply thin film of coating material to the interiorof the can. The cans are dried in bulk in a curing oven. An operatorfeeds the cans to the coaters. The cans are inspected for proper coatingand then placed into the final packaging containers.

The batch and queue process described above has several disadvantages.The narrow strip stock produces significant scrap, due to unusablematerial at the edge of the strip. The required coil changes to feed thenarrow strip stock to the redraw press lead to inefficiencies inoperation. Damage can occur due to parts contacting other parts in thebatch containers. Rejection of parts due to dimensional, coating andcosmetic defects may be inconsistent due to using different inspectors.

Another disadvantage is the requirement to follow the parts produced bya particular tool through the manufacturing process by keeping track ofthe batch container corresponding to each tool. This is necessary inorder to halt operation from a particular redraw press and takecorrective action if dimensional changes occur due to tool wear. Manualoperator time is required to move batch containers from one operation tothe next while retaining identification of the batch with the toolproducing the part.

Accordingly, one object of the present invention is to provide acontinuous high volume process for coating and inspecting the coating ondrawn metal parts.

Another object of the invention is to provide an improved continuousprocess for tracking drawn metal parts through coating operations so asto identify the coating gun that coated the parts.

Still another object of the invention is to provide an improved processfor inspecting coated parts and taking corrective action to shut downthe coating gun if the coating is defective.

Another object of the invention is to provide an improved process forcoating and inspecting the coating on drawn metal parts, andsubstituting additional coating guns if a coating gun is defective.

SUMMARY OF THE INVENTION

Briefly stated, the invention concerns a process for coating andinspecting drawn metal parts, comprising the steps of: providing asingle ordered stream of drawn metal parts having a repeating sequentialorder, said repeating sequential order enabling identification of thedrawn metal part by the location of the drawn metal part in said orderedstream; conveying said ordered stream with continuous movement of thedrawn metal parts; converting the movement of the ordered stream into anintermittent motion having a move time and a dwell time; providing aplurality of coating guns; coating pre-selected portions of a selecteddrawn metal part during a first dwell time with a first coating gun;providing automatic inspection means for determining if the coating isdefective; inspecting the coating of said selected drawn metal part withsaid automatic inspection means during a second dwell time; shuttingdown said first coating gun if the coating is defective, said selectedcoating gun being identified by the location of the removed drawn metalpart in the ordered stream; and enabling a second coating gun to coatdrawn metal parts in the same sequential location in the ordered streamthat was previously assigned to the first coating gun. The enabling stepis preferably carried out by firing the second coating gun at twice itsnormal firing rate, including shifting the position of the secondcoating gun in some cases.

DRAWING

The invention will be better understood by reference to the followingdescription, taken in connection with the accompanying drawing, inwhich:

FIG. 1 is a simplified block diagram of the manufacturing process,

FIG. 2 is a schematic representation of a merge and sequence machine,

FIG. 3 is a schematic representation of portions of a conveyor, withmeans to remove a part for inspection,

FIG. 4 is a schematic representation of apparatus used to coat drawnmetal parts,

FIG. 5 is a schematic diagram of the packing process, and

FIG. 6 is a perspective view of a computer generated model showing theactual placement of equipment, with simplified diagram of the processcomputer controls.

GENERAL DESCRIPTION OF THE PROCESS

Referring to FIG. 1 of the drawing, a coil payoff system 10 feeds acupping press 12 with a wide strip of thin metal from a coil. Cuppingpress 12 performs a blanking and drawing operation to produce seven cupsat a stroke, which are fed onto a magnetic conveyor 14. The flow ofparts from the cupping press 12 divide into two “cells” A and B. Eithercell A or B may operate independently of the other throughout much ofthe manufacturing process, even though they rejoin to share someequipment toward the end of the process.

Conveyor 14 supplies the cups to redraw presses 16, 18 in cell A and toredraw presses 20, 22 in cell B. In order to provide for possibledowntime of cupping press 12 and/or redraw presses, part accumulators24, 26 act as buffers to receive or discharge cups as necessary.Accumulators 24, 26 are towers with helical tracks for temporary storageof parts with control means to switch parts to the presses if thecupping press is not operating, but any type of storage capable ofaccumulating and discharging parts via conveyors will be suitable.

The redraw presses 16, 18, 20, 22 each are equipped with at least twosets of redraw stations, hereinafter defined “tools”. As defined in thispatent application, a “tool” (singular) is actually a set comprisingseveral redraw punches and dies, which successively draw the cups intothe final dimensional shape of a battery can and cut off the top rim ofthe can. Thus, in the illustration shown, each press handles two “tools”and, therefore, produces two parts during each stroke. However, morethan two tools per press are also possible.

Battery cans from each of the tools in each of the redraw presses aredischarged onto a separate conveyor, such as that indicated by referencenumber 28. Means are provided to remove a sample for local inspection asshown at 30. While a single conveyor 28 and its inspection station 30are indicated on the drawing for tool number four of redraw press 18, asimilar arrangement is placed at the tool discharge of each redrawpress. If there are more than tools in each redraw press, additionalconveyors will be required, one for each tool.

Battery cans 1, 2, 3, 4 from presses 16, 18 in cell A are separatelyaccumulated in four serpentine tracks, one for each tool, in anaccumulator 32. Similarly battery cans 5, 6, 7, 8 from redraw presses20, 22 in cell B are separately accumulated in four serpentine tracks inaccumulator 34.

A special ordered merge device 36 in cell A and an identical device 38in cell B perform an ordered merge operation to be described later indetail. Briefly the separate streams of parts from the tools of each ofthe presses are merged into a single ordered stream of parts maintaininga sequential order that enables identification of the tool by thelocation of the part in the stream. This ordered stream of parts isrepresented by the dashed lines 40–42 representing the conveyors fromthe ordered merge 36, 38.

An automatic dimensional inspection machine 44 is shared by both cells Aand B and equipped with instruments, which measure certain criticaldimensions in the battery cans. Part ejectors 46, 48 are preciselycontrolled to remove a part from a pocket on a conveyor 40, 42 and placeit in the dimensional inspection equipment 44. It is important to notethat the empty pocket in the conveyor from which the part is removed ismaintained throughout the manufacturing process, so that the integrityof the ordered stream is maintained as the battery cans move through theprocess. This integrity is maintained when parts are transferred fromone conveyor to the next.

Battery cans from cell A and cell B are conveyed to washer/dryers 50, 52respectively. There, the drawing compound is removed and the batterycans dried. Thereafter, each washer/dryer 50, 52 supplies a buffer 54,56 respectively. Buffers 54, 56 are maintained half-full by a moveablebridge mechanism. The buffer level controls the speed of thecoating/inspection conveyor downstream of it.

Optical camera inspection systems 58, 60 measure the streams of batterycans from the buffers 54, 56. The parts are fed in order maintaininggaps for any missing parts, onto special motion converting conveyors 62,64 equipped with coating guns. These devices will be described furtherin detail, but, briefly stated, the continuously moving stream of partsis converted to an intermittently moving or indexed motion having adwell time and a move time. During the dwell time, the cylindricalbattery cans are rotated while they are sprayed on the inside withcoating guns. Following the coating operation, an automatic opticalinspection system at 66, 68 inspects internal coating, and any cosmeticanomalies on the exterior of the battery can. Rejects are automaticallyremoved by part ejectors 70, 72. The parts, still segregated in therespective conveyor pockets for the two cells A, B move to a coatingdryer 74 and, from there, to the pack operation indicated at 76.

Ordered Merge Operation

While the preceding section describes the overall process formanufacturing drawn metal parts in a general discussion, several aspectsof the process will be described in detail. One of these is the orderedmerge operation, which combines the separate streams of parts from theseparate drawing press tools in such a way that the sequence is alwaysthe same and is repeated periodically. In this way, the segregatedstream of parts are merged into a single ordered stream of drawn metalparts having a sequential order which enables identification of thedrawing press tool in which the part was made.

FIG. 2 illustrates in simplified diagrammatic fashion the ordered mergeoperation. It will be understood that the actual configuration will varyaccording to size and type of the parts, as well as variations in thecomponents. The ordered merge machine is shown generally at 80 andcomprises four separate accumulating receptacles 82, 84, 86, 88. Theseare part of the accumulators 32 or 34 shown in FIG. 1. Each suchaccumulating receptacle receives drawn metal parts from a differenttool, in this case parts 1, 2, 3 and 4 coming from tool one, tool two,tool three, and tool four respectively of presses 16, 18 (FIG. 1).Whenever parts 1, 2, 3 and 4 are depicted in the following drawings,they are deemed to be from their corresponding source tool, althoughthey may appear at different places in the processes to be described.Accumulating receptacles 82, 84, 86, 88 supply feed wheels 90, 92, 94,96 respectively. The feed wheels supply parts to a merge wheel 98 whichfeeds a conveyor 100. The feed wheels have pockets, such as 102, and themerge wheel 98 has pockets, such as 104. The feed wheels aremechanically geared to the merge wheel, so that a pocket 102 on an feedwheel registers with every fourth pocket 104 on the merge wheel as thewheels turn.

If there are more than two tools on each redraw press, e.g., threetools, the feed wheels and index wheels must be modified accordingly toinclude the proper number of pockets.

Conveyor 100 is designed to have a carrier belt 106, with dividing walls108 providing segregated pockets 110. The speed of the conveyor 100 istimed to coincide with the speed of the merge wheel 98, so that thepockets 104 on the merge wheel feed the segregated pockets 110 on theconveyor in precise order. FIG. 2 illustrates that accumulatingreceptacle 86 was temporarily empty, so that feed wheel 94 waspreviously not feeding parts 3 to the designated pocket on merge wheel98. Therefore the segregated pockets 110 on conveyor 100 are temporarilyempty, but the single ordered stream of parts continues to flow to thenext intermediate processing operation.

Part Ejectors

The process provides for removal of parts at various points of theprocess for dimensional inspection, for local tool maker inspection, fordefects located at any point in the process. Such part ejectors areshown on FIG. 1, for example, at 29, 46, 48, 70, 72. FIG. 3 illustratesschematically, in simplified form, the operation of such a part ejector.A conveyor 112 is made up of articulated links 114 hinged together atpivot points (not shown). Each such link has a divider wall 116projecting upwardly from the link platform. The space between dividerwalls 116 provides segregated pockets for the parts 1, 2, 3, 4 supportedon the platforms of the articulated links 114. The drawn metal parts arecylindrical and each has an open end 118, as is typical of battery cansand similar drawn parts.

Removal of parts is accomplished with an air jet 120 having a tip 122aligned with the open end of the parts, and a collection tube 124 havingan open end 126 aligned with the axis of the air jet. The collectiontube is provided with directed openings 128 which are, in turn,surrounded by a manifold 130. When it is desired to remove a part, airjet 120 and manifold 130 are supplied with a blast of high pressure air,pushing the part 3 into the open end 126 of the collection tube 124. Airentering the manifold 130 and openings 128 propels the part 3 throughthe tube to a collection point (not shown).

This arrangement is known as a “bazooka”, and may be eitherautomatically or manually actuated to remove a part from a segregatedpocket. Since the parts are in sequence, the part corresponding to anyselected tool source may be removed. The location of the pocket on theconveyor is a function of the conveyor speed which is precisely known byan encoder, and controlled by a programmed logic computer (see FIG. 6).

Coating Operation

Referring to FIG. 4 of the drawing, a conveyor 132 is provided with aknown type of mechanism (not shown) to convert a continuous movement toan indexed movement having a move time and a dwell time. The coatingoperation involves spraying a conductive coating into the open ends ofthe drawn metal parts. Coating is accomplished by means of coating sprayguns A, B, C, D. These are spaced along conveyor 132, which is movingfrom left to right in the drawing, so that each spray gun isautomatically actuated to spray a jet of coating material into the openend of the part during the dwell time of conveyor 132. Rotatingapparatus (not shown) is also provided to rotate the cylindrical partsabout their axis while the spray gun is active so as to obtain a uniformcoat. Spray guns A, B, C, D are spaced along conveyor 132, so thatcoating gun A coats the inside of part 1, coating gun B coats the insideof part 3, coating gun C coats the inside of part 4, and coating gun Dcoats the inside of part 2.

Because of the possibility that one or more coating guns may becomeinoperative, a unique system is employed to enable a coating gun to takeover the job of an inoperative coating gun, while continuing to processits previously assigned part. The coating guns are capable of firingtwice as fast as their normal firing rate. Also, coating guns B and Care able to shift one position along conveyor 132 to the alternaterespective positions indicated by reference letters B′, C′.

Method 1: If gun B should become inoperative, it will be observed thatcoating gun A may be operated at twice its normal firing rate to coatparts 1 and 3. Similarly, gun B may take over for gun A should gun Abecome inoperative. In a similar manner, guns C and D may assume theduties for each other by firing at twice the normal rate.

Method 2: Should both guns C and D become temporarily inoperative, gun Bmay be shifted to position B′. With both guns A and B′ firing at twicethe normal rate, they can take over the job of coating all four parts.In a similar manner if both guns A and B become temporarily inoperative,gun C may be shifted to C′ and guns C′ and D, firing at twice the normalrate will coat all four parts.

The coated parts are inspected by an optical inspection system 134 andremoved by a parts ejector 136 if they should be unacceptable.

Packing Segregated by Tool

Referring to FIG. 5 of the drawing, a packing area shown generally as138 receives an ordered stream of parts 1, 2, 3, 4 on a conveyor 140from cell A and a second ordered stream of parts 5, 6, 7, 8 on aconveyor 142 from cell B. In keeping with the philosophy of theinventive process, some of the pockets of the conveyors may be emptybecause of removal of parts upstream for various purposes. A series ofreceptacles 144 are provided, each one from a different tool. A U-shapedconveyor 146 carries boxes of parts from a box filling area showngenerally as 148 to a box collection area shown generally as 150.

Empty boxes are supplied along a first table (or conveyor) 152. Boxesbeing filled are stationed along a second table (or conveyor) 154 and,when full, are pushed onto conveyor 146. The filled boxes are thenconveyed to a specific collection station, such as the one designated at156. From there they are removed for shipment, the boxes being coded todesignate the source tool from which they were manufactured.

Dimensional Test Unit

Referring to FIG. 1 of the drawing, dimensional inspection is carriedout by dimensional test unit 44. This unit is designed to measure, viatouch probes, pre-defined dimensions on the parts. The unit will measureparts from eight tools plus allowance for manual insertion/inspection ofparts. The unit provides for measuring, indexing and discharge of parts.A detailed description of the device as used to measure that parts isbeyond the scope of this application. However, such devices are known inthe prior art. Part ejectors such as previously mentioned in connectionwith FIG. 3 are attached to conveyors feeding the washer/dryers 50, 52,as indicated at 46, 48 in FIG. 1. The parts are introduced vertically,closed end down. An electromagnetic brake holds the part momentarily,and then releases the part into the pocket in the dimensional test unit44. When the dimensional test unit is in automatic mode, parts arerequested for dimensional measurement in a pre-selected sequence. Asignal is received from an encoder on the conveyor informing it that therequested part is positioned in front of the part ejector. The partejector is activated and the part enters the dimensional test unit.

The dimensional test unit measures a part approximately every 10seconds. If eight tools are running, there will be an 80 second delaybetween the time a part is measured and the time a part from the sametool is measured again. If a defective part is detected, a second partfrom the same tool should be requested as soon as possible to verify theoriginal result. Since the line is continuing to move, there could be aconsiderable number of defective parts downstream, as well as thoseupstream from the defective tool. The dimensional test unit sends theappropriate signals to stop the press with the defective tool, to stopthe discharge conveyor from the appropriate buffer 54, 56, and toactivate appropriate parts ejectors to purge the line of all parts fromthat tool, both upstream and downstream. Corrective action on thedefective tool may then be taken, while the line continues to run,maintaining empty pockets corresponding to those pre-selected for thatparticular tool.

Process Speed Control

The manufacturing system includes various safeguards and control devicesto maintain production of drawn metal parts in an optimum manner, andmaximize overall production, while assuring that failure or defectiveoperation of any piece of equipment does not shut down the entire line.Reference to FIG. 6 shows a perspective view of the actual configurationof the production line. Only cell A is indicated on the drawing, alongwith apparatus that is shared by cells A and B. The reference numbers ofthe pieces of equipment correspond to those in FIG. 1. A programmedlogic computer 158 is representative of one or more programmed logiccomputers receiving signals and sending commands represented by phantomlines. Any deficiency in cups from the cupping press that is detected at160 is communicated over lines 162 to controls for the spiral towerbuffer 24 to augment the supply. Shortage of parts in the buffer 24signals cupping press 12 over line 164.

Press strokes per minute of the four redraw presses are detected andcommunicated to PLC 158 over lines 166, 168. Press stroke speeds areused in a computer program to set the speed of washer/dryer 50 overcontrol line 170. The speed of the discharge from buffer 54 and thewasher/dryer discharge is set to vary in accordance with the capacitylevel of the buffer, speeding up as the buffer level of parts lowers andslowing down as it fills up. This is indicated by control line 172. Themerge wheel for ordered merge unit 36 is directly driven by the washer50. Any back-up of parts into the separately fed accumulators 32 isdetected at 174 and shuts down the appropriate press. The coating linesand their associated conveyors 62 are controlled by the speed of thedischarge conveyor from buffer 54, as indicated by control line 176.

Therefore, it can be seen that by provision of appropriate accumulatorsand buffers at various stages in the process, as well as controlling theconveyor speed of intermediate upstream or downstream processing units,the continuous in-line process can continue to operate at optimum speed.This is despite the removal of parts at various points in the processfor inspection or due to faulty manufacture.

Other modifications of the invention will become apparent to thoseskilled in the art and it is desired to cover in the appended claims allsuch modifications as fall within the true spirit and scope of theinvention.

1. Process for coating and inspecting drawn metal parts, comprising thesteps of: (a) providing a single ordered stream of drawn metal partshaving a repeating sequential order, said repeating sequential orderenabling identification of the drawn metal part by the location of thedrawn metal part in said ordered stream; (b) causing said ordered streamto move with an intermittent motion having a move time and a dwell time;(c) providing a plurality of coating guns firing at normal firing ratesduring said dwell times, wherein said plurality of coating guns comprisea first coating gun assigned to coat drawn metal parts in a firstsequential location in the ordered stream and a second coating gunassigned to coat drawn metal parts in a second sequential location inthe ordered stream; (d) coating a pre-selected portion of a selecteddrawn metal part during a first dwell time with the first coating gun;(e) providing automatic inspection means for determining if the coatingis defective; (f) inspecting the coating of said selected drawn metalpart with said automatic inspection means during a second dwell time;and (g) enabling the second coating gun to coat drawn metal parts inboth the first sequential location in the ordered stream that waspreviously assigned to be coated by the first coating gun and in thesecond sequential location in the ordered stream if the inspectedcoating is defective.
 2. The process according to claim 1, wherein saidenabling step (g) comprises firing the second coating gun at twice saidnormal firing rate.
 3. The process according to claim 1, wherein saidenabling step (g) comprises shifting the position of said second coatinggun along said ordered stream and also firing the second coating gun attwice said normal firing rate.
 4. Process for coating and inspectingdrawn metal parts, comprising the steps of: (a) providing a singleordered stream of drawn metal pans having a repeating sequential order,said repeating sequential order enabling identification of the drawnmetal part by the location of the drawn metal part in said orderedstream; (b) causing said ordered stream to move with an intermittentmotion having a move time and a dwell time; (c) providing a plurality ofcoating guns operating at normal firing rates during said dwell times,wherein said plurality of coating guns comprise a first coating gunassigned to coat drawn metal parts in a first sequential location in theordered stream and a second coating gun assigned to coat drawn metalparts in a second sequential location in the ordered steam; (d) coatinga pre-selected portion of a selected drawn metal part during a firstdwell time with the first coating gun; (e) providing automaticinspection means for determining if the coating is defective; (f)inspecting the coating of said selected drawn metal part with saidautomatic inspection means during a second dwell time; (g) shutting downsaid first coating gun if the coating is defective, said selectedcoating gun being identified by the location of the removed drawn metalpart in the ordered stream; and, (h) enabling the second coating gun tocoat drawn metal parts in both the first sequential location in theordered stream that was previously assigned to be coated by the firstcoating gun and in the second sequential location in the ordered stream.5. The process according to claim 4, wherein said enabling step (h)comprises firing the second coating gun at twice said normal firingrate.
 6. The process according to claim 4, wherein said enabling step(h) comprises shifting the position of said second coating gun alongsaid ordered stream and also firing the second coating gun at twice saidnormal firing rate.